Making Measurements
Operational Hints
4-52
Using the LI-6400
4
Controlling Low Flow Rates
When the 6400-01 CO
2
Mixer is installed, flow control is done with a flow
diverter (Figure 4-15). The excess flow from this device is dumped into the
reference leg, providing faster response times in the reference IRGA.
(The complete schematic is in Figure 20-9 on page 20-36). However, when
the flow control unit is routing most of the flow to the reference cell, there
comes a point when some of that flow comes
back
through the flow divider
and in fact goes to the sample cell. Typically with the 6400-01 CO
2
Mixer,
the lowest attainable flow is about 20 or 30 µmol s
-1
.
If low flows are needed for some special experiment, this behavior can be pre-
vented quite simply by replacing the ÒYÓ connector with a straight union
(Figure 4-16), and letting the flow from the flow controller vent to the atmo-
sphere. This will allow precise flow control down to 0, but at the expense of
horrendously slow response times in the reference IRGA at these low rates.
divider
flow meter
75%
25%
To Reference
To Sample
Flow Control
Figure 4-15. Flow schematic for units with a 6400-01 CO
2
mixer. Flow control is
done with a diverter valve, and the excess flow is dumped into the reference flow.
divider
flow meter
75%
25%
To Reference
To Sample
Flow Control
Replace ÒYÓ with straight union
Figure 4-16. To achieve flow control down to zero, replace the T downstream of the
diverter with a straight union.
Summary of Contents for LI-6400
Page 1: ...Using the LI 6400 Portable Photosynthesis System ...
Page 15: ...Part I The Basics ...
Page 16: ......
Page 174: ...Making Measurements Answers to Questions 4 56 Using the LI 6400 4 ...
Page 175: ...Part II Useful Details ...
Page 176: ......
Page 200: ...Standard Tools Power ON Hooks 5 24 Using the LI 6400 5 ...
Page 214: ...Real Time Data Real Time Graphics 6 14 Using the LI 6400 6 ...
Page 234: ...Environmental Control Light Control 7 20 Using the LI 6400 7 ...
Page 244: ...Light Sensor Considerations Gallium Arsenide Phosphide GaAsP Sensor 8 10 Using the LI 6400 8 ...
Page 288: ...Data Logging Making Your Own AutoPrograms 9 44 Using the LI 6400 9 ...
Page 289: ...Part III Working With Files ...
Page 290: ......
Page 312: ...The LPL File System Troubleshooting 10 22 Using the LI 6400 10 ...
Page 340: ...Downloading Files Using a Data Capture Program 11 28 Using the LI 6400 11 ...
Page 375: ...Part IV Configuration Issues ...
Page 376: ......
Page 420: ...Defining User Variables Old Style vs New Style 15 18 Using the LI 6400 15 ...
Page 454: ...Using an Energy Balance Further Reading 17 12 Using the LI 6400 17 ...
Page 455: ...Part V Maintenance Troubleshooting ...
Page 456: ......
Page 572: ...Troubleshooting Useful Information 20 46 Using the LI 6400 20 ...
Page 593: ...Part VI Programming ...
Page 594: ......
Page 622: ...Programming with LPL Compiler Directives 22 28 Using the LI 6400 22 ...
Page 846: ...Index I 16 Using the LI 6400 ...